The article by A. Ishibashi: xe2x80x9cII-VI Blue-Green Laser Diodesxe2x80x9d IEEE Journal of Selected Topics in Quantum Electronics, Vol. 1, pp. 741 to 748 (1995) provides an overview of the use of II-VI semiconductor material for the production of laser diodes which emit blue or green light. ZnMgSSe, ZnCdSe or ZnSe and ZnTe is specified as the material. An MQW structure made of ZnTe/ZnSe is also mentioned. JP-A 7-66 494 and U.S. Pat. No. 5,268,918 describe beryllium-containing semiconductor compositions for the production of laser diodes emitting blue or green. U.S. Pat. No. 5,422,902 and the articles by P. M. Mensz: xe2x80x9cBeTe/ZnSe graded band gap ohmic contacts to p-ZnSexe2x80x9d Appl. Phys. Lett., Vol. 64, pp. 2148 to 2150 (1994) and by R. G. Dandrea et al.: xe2x80x9cDesign of ohmic contacts to p-ZnSexe2x80x9d Appl. Phys. Lett., Vol. 64, pp. 2145 to 2147 (1994) describe the use of a graded sequence of layers of BeTe and ZnSe for the production of contact layers between an active layer and a metallic connection contact.
The structures and materials described in the cited publications have a variety of disadvantages which have an adverse effect on the use for laser diodes. The difficulties arising when using ZnSe are that the growth of such layers on a GaAs substrate is disturbed, that a poor transport of charge carriers takes place via the interface between the II-VI semiconductor and the III-V semiconductor, and that good lattice matching of ZnTe to GaAs is not possible, for example, owing to the difference in the lattice constants. In addition, good ohmic contact to metals cannot be produced on ZnSe having p-conducting doping.
The object of the present invention is to specify an optoelectronic component for radiation generation, in particular in the green and blue spectral region, which can be produced comparatively easily together with good functionality and a long service life. In particular, the intention is to overcome the difficulties which exist in the current prior art and have been partly described in the introduction.
In general terms, the present invention is an optoelectronic component on a substrate made of a material selected from the group of GaAs, InP, InGaAs, Si, Ge, GaP and ZnSe. An active layer is provided for radiation generation in which the active layer is formed a by a sequence of layers of alternating composition as a potential well (quantum well) with a superlattice. In this sequence of layers, a layer made of a beryllium-containing chalcogenide and a layer made of a II-VI semiconductor material having a different composition respectively succeed one another. The active layer is arranged between layers which are doped for electrical conductivities with mutually opposite signs and which have contacts to provide electrical connections for these layers.
Advantageous developments of the invention are as follows.
The beryllium-containing chalcogenide is BeTe, BeS or BeSe or a solid-solution composition which contains Be and Te or Be and Se or Be and S.
The beryllium-containing chalcogenide is BeTe and the II-VI semiconductor material having a different composition is ZnSe or ZnCdSe.
The active layer is arranged between barrier layers made of beryllium-containing chalcogenide.
The present invention is also an optoelectronic component. A layer of BeZnCdSe or BeZnCdS, which is provided for radiation generation, is arranged between layers which are doped for electrical conductivities having mutually opposite signs and have contacts to provide electrical connections for these layers.
Advantageous developments of this embodiment of the present invention are as follows.
The BeZnCdSe or BeZnCdS contain at least 3 atomic percent of beryllium.
The present invention is also an optoelectronic component on a substrate made of a material selected from the group of GaAs, InP, InGaAs, Si, Ge, GaP and ZnSe. An active layer is provided for radiation generation and is arranged between barrier layers. At least one mantle layer is made of a beryllium-containing chalcogenide. The mantle layer comprises a sequence of layers which are alternately made of beryllium-containing chalcogenide and a further II-VI semiconductor material and which form a superlattice.
The mantle layer is arranged between the active layer and the substrate. A buffer layer made of a beryllium-containing chalcogenide is arranged between the mantle layer and the substrate. The sequence of layers in the mantle layer adjoining this buffer layer forms a superlattice, and, at a distance from the buffer layer, the thicknesses of the layers made of beryllium-containing chalcogenide decrease in one direction. The thicknesses of the layers made of the further II-VI semiconductor material increase in this direction.
The substrate is III-V semiconductor material or silicon. The mantle layer is applied as a buffer layer to this substrate.
The mantle layer is arranged between a layer of GaAs or a substrate of GaAs or Si and a layer of II-VI semiconductor material.
The present invention is also an optoelectronic component on a substrate made of III-V semiconductor material or silicon, having an active layer which is provided for radiation generation and is arranged between barrier layers. A buffer layer containing BeTe is applied to the substrate.
The active layer and the barrier layers are either II-VI semiconductor materials or III-V semiconductor materials.
There is provided, on both sides of the active layer, a mantle layer which contains a sequence of layers which are alternately a beryllium-containing chalcogenide and a II-VI semiconductor material differing therefrom. The mantle layers form Bragg reflectors which act vertically with respect to the layer planes.
The present invention is also an optoelectronic component on a substrate made of a material selected from the group of GaAs, InP, InGaAs, Si, Ge, GaP and ZnSe. An individual layer of BeTe is provided between the substrate and a layer provided for radiation generation.
The substrate has n-conductive doping.
In order to form light-emitting diodes or laser diodes, the component according to the invention uses a layer structure of II-VI semiconductor material incorporating at least one beryllium-containing chalcogenide, which is to be understood as meaning a beryllium chalcogenide or a solid-solution composition based on a beryllium chalcogenide. Preferred chalcogens are Te, Se and S. In the text below, therefore, xe2x80x9cberyllium-containing chalcogenidexe2x80x9d refers to any desired salt, in particular a salt containing S, Se or Te, which contains Be as a cation or Be and as many other cations such as, for example, Mg or Zn, as desired. Preferred embodiments provide, in particular, a combination with ZnSe and with a GaAs substrate. However, it is also possible to use other substrates such as, for example, InP, InGaAs, ZnSe, Si, Ge, GaP or the like. BeTe, BeSe, BeS and solid-solution compositions of these beryllium chalcogenides with semiconductor materials such as, for example, ZnSe, ZnS, ZnTe and MgSe appear to be suitable, in particular, for the active layer or layer structure, as well as for mantle layers, which are to be understood in the text below and in the claims as meaning buffer layers, (additional) barrier layers (confinement layers), (also passive) waveguide layers, lattice layers, covering layers and layer portions or combinations of such layers. In addition, in the text below, II-VI semiconductor material can always refer specifically to a (further) beryllium-containing chalcogenide. Different embodiments are described in detail below with reference to the Figures.